Current sensing is sometimes used in feedback control loops to regulate operation of a circuit. For example, voltage regulators, such as DC-DC converters, often use current feedback control, whereby a signal based on the sensed current of the DC-DC converter output is used to ensure that the voltage applied at the output remains regulated within specified limits. Current can be sensed based on a current or a voltage. Current sensing based on a voltage is referred to as voltage-mode current sensing. A typical voltage-mode current sensing technique is to insert a sense resistor along the path of the current to be sensed to obtain a voltage signal. However, this voltage-mode current sensing technique can be undesirable, particularly in high-current applications, due to the power consumption caused by the sense resistor.
Current sensing based on a current is referred to as current-mode current sensing. A drawback of current-mode current sensing techniques is that the level of the sensed current can be affected by the resistive load of the feedback path, thereby limiting the accuracy of the current sensing. Accordingly, there is a need for an improved current sensing technique.